A conventional water filter apparatus mainly comprises a filer cartridge and a coupling device. The coupling device is placed between a water supply and the filter cartridge for connecting the water supply to the filter cartridge. There are two openings in the coupling device. One is a water inlet opening and the other is a water outlet opening. The water inlet opening is connected to a water tap and the water outlet opening is connected to another independent water supply tap where the filter cartridge is placed underneath the coupling device.
After turning on the water tap for inserting water into the coupling device, drinkable water comes out of the independent water supply tap through the filtering material of the filter cartridge. In a conventional assembly of the coupling device and the filter cartridge, an outer thread is formed on the outer casing of the filter cartridge and an inner thread is formed on the coupling device. By firmly and securely fastening the filter cartridge to the coupling device, water flows through the filter cartridge via the coupling device.
The conventional assembly of the coupling device and the filter cartridge has at least the following disadvantages:
1. If the inner thread of the filter cartridge and the outer thread of the coupling device are not tightly coupled with each other, water may leak. PA1 2. If the connection between the filter cartridge and the coupling device is loose, the filter cartridge may fall off when the water pressure is suddenly increased. PA1 3. In the process of replacing the filter cartridge, a user must remember to turn off the water supply. Otherwise, the water runs out widely.